We will probe the interactions between the retinal chromophore and rhodopsin by means of specific modification of several amino acids. The reactivities of these amino acid residues in rhodopsin, opsin, and denatured rhodopsin will be compared. The retinol-binding protein from human plasma will be investigated as a model for rhodopsin. The primary amino acid sequence, the low temperature absorption and circular dichroism spectra, and the amount of the protein in various retinal diseases will be determined. Antibodies to a site specific locus on the rhodopsin molecule will be developed and used to probe the localization of the molecule in the rod outer segment discs. An attempt will be made to assemble ROS discs from purified components: rhodopsin, other protein and phospholipids in order to be able to assess the contribution of each to the assembled membrane. The technique of circular and linear dichroism, resonance enhanced Raman spectroscopy and magnetic circular dichroism will be used to investigate the various intermediates of illuminated rhodopsin. Rapid volume changes and ionic fluxes in rod outer segment discs will be measured in an attempt to describe the action of light on these membranes.